/Engine/Source/Runtime/Engine/Classes/Engine/SkeletalMesh.h
Return true if the imported data is present. Return false otherwise. Old asset before the split workflow will not have this data and will not support import geo only or skinning only. This value is cache in the LODModel and update when we call SaveLODImportedData.
bool IsLODImportedDataEmpty ( const int32 LODIndex ) const